Researchers digging deeper into the origins of the Sutter’s Mill meteorite, which exploded over California’s Gold Country in 2012, have found diamonds and other “treasures” that provide important new insight into the early days of our solar system. They report their results in 13 papers in the November issue of Meteoritics & Planetary Science.

UC Davis scientists Akane Yamakawa and Qing-Zhu Yin in the Department of Earth and Planetary Sciences studied the different forms of the element chromium, called isotopes. They found that at least five different stellar sources composed of mixtures of 54-chromium-rich and -poor materials must have contributed matter to the nascent solar system four and half billion years ago. Some of these materials remained in the Sutter’s Mill meteorite.

Fragments of the Sutter's Mill meteorite (NASA photo).

“The formation of the solar system did not fully erase and homogenize these signatures, and Sutter’s Mill provides the clearest record yet,” said Yin, who co-led the Sutter’s Mill Meteorite Consortium with Peter Jenniskens of NASA Ames and the SETI Institute.

In primitive meteorites like Sutter’s Mill, some grains survive from what existed in the cloud of gas, dust and ices that formed the solar system. In Sutter’s Mill, the liquid water appears to have destroyed the silicate type of these, according to Xuchao Zhao of the Chinese Academy of Sciences, working with NASA and UC Davis colleagues.

Researchers in the consortium also found two, 10-micron diamond grains in the meteorite. Though too small to sparkle in a ring, they were larger than the nanometer-sized diamonds commonly found in such meteorites. Nanodiamonds are thought to originate in the atmospheres of stars. The larger diamonds found in Sutter’s Mill may have had another origin closer to home.

“We suspect that these diamonds are so-called xenoliths,” said Yoko Kebukawa, recently of Hokkaido University, Japan. “Bits and pieces that originated in the interior of other much larger parent bodies.”

The Sutter’s Mill meteorite fell just 60 miles from the UC Davis main campus. Scientists from UC Davis, including Yin, immediately traveled to the site with students and colleagues looking for specimens and reaching out to the public to provide meteorite donation for science.

Yin confirmed that the main mass was carbonaceous chondrite – one of the rarest types to hit the Earth and containing cosmic dust and presolar materials that helped form the planets of the solar system. The meteorite’s main mass was X-rayed by CT scan at UC Davis, and the university acquired a portion of this mass.